Ventilation devices are used in fuel tanks of motor vehicles in order to remove from the tank gases which arise in the tank during the operation thereof or during refuelling of the tank (venting), or to supply required gases, especially air, to the tank (gas admission). For this purpose, ventilation lines are passed out of the tank, and the gases are passed, via intermediate stages such as vapour traps and compensation tanks, for example, to the outside, generally via a fuel vapour filter, such as an activated carbon filter. In this context, it is possible to envisage valves which open a ventilation line exclusively during a refuelling operation (refuel ventilation line) or which open a ventilation line exclusively or additionally during normal operation of the tank device (service ventilation line).
It is known, e.g. from DE 10 2006 004 630 A1, that a connection to a filler pipe may be provided between a refuel ventilation line and the fuel vapour filter, said connection being referred to as a recirculation opening or as a recirculation channel. Via a recirculation channel of this kind, it is possible for some of the gases displaced from the tank during refuelling to recirculate through the filler pipe into the tank.
It is also possible to use a connection from a ventilation line to the filler pipe for on-board diagnosis (OBD), for example.
If a ventilation device has a fluid-carrying connection between a ventilation line and a filler pipe, however, there is the problem that, if the fuel pump nozzle allows continued flow, i.e. if there is a malfunction that causes the fuel pump nozzle not to shut off, fuel can pass from the fuel pump nozzle, via the filler pipe and the fluid-carrying connection, to the ventilation line and thus onward to a fuel vapour filter, for example.